Subject: [Hipsec] Identifying SIP user agents

From: [email-masked] (Gonzalo Camarillo)
Date: Tue Feb 24 02:58:01 2004

Folks,

one of the goals of the HIP WG is to help other communities understand 
the implications of introducing this technology in the net. Here we have 
a situation where the multimedia community could benefict from the HIP 
work, or at least, from some of our ideas.

The SIPPING WG is working on defining global identifiers for SIP 
(Session Initiation Protocol) user agents. That is, my SIP phone will 
have a global identifier, so that I can distinguish it from my other SIP 
devides (like my software based SIP user agent running in my laptop). 
the relevant drafts are:

http://www.ietf.org/internet-drafts/draft-stucker-sip-guid-00.txt
http://www.ietf.org/internet-drafts/draft-jennings-sipping-instance-id-00.txt

The multimedia community was wondering whether they could use HIs or 
HITs for this purpose. They will welcome your comments.

Thanks,

Gonzalo

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From: [email-masked] (senthil ayyasamy)
Date: Tue Feb 24 03:38:01 2004

At 10:41 AM 2/24/2004 +0200, Gonzalo Camarillo wrote:
>The SIPPING WG is working on defining global identifiers for SIP (Session 
>Initiation Protocol) user agents. That is, my SIP phone will have a global 
>identifier, so that I can distinguish it from my other SIP devides (like 
>my software based SIP user agent running in my laptop). the relevant 
>drafts are:
>

without looking into the drafts, how it is different from globally routable 
UA URI?

>The multimedia community was wondering whether they could use HIs or HITs 
>for this purpose.

It can use if we solve the referral/rendezvous issue(i.e. SIP can use HI 
instead of IP
address.)

I have two questions about rendezvous/referral:

1. If HIPRR come up with a better-than-DNS naming resolution system, can 
applications bypass
    DNS and directly access the new system? It will be useful for many 
future applications
    like ad-hoc, sensor, P2P etc.

2. I was looking into draft-ietf-dnsext-mdns today. what are your views 
about LLMNR _like_
    model + distributed object look-up for name resolution?

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From: [email-masked] (Gonzalo Camarillo)
Date: Tue Feb 24 03:43:01 2004

Hi,

> without looking into the drafts, how it is different from globally 
> routable UA URI?

A globally routable URI is a URI that routes to a particular user agent 
in the context of a *dialog*. That is, while I am in a session with you, 
you can use that URI to reach me. These type of URIs are generated by 
the server.

> It can use if we solve the referral/rendezvous issue(i.e. SIP can use HI 

The global identifiers we are looking for do not even need to be 
routable. That is, it can be a sequence of bits that identify a UA. SIP 
provides other mechanisms to be able to contact such a UA.

Gonzalo

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From: [email-masked] (senthil ayyasamy)
Date: Tue Feb 24 04:06:00 2004

At 11:26 AM 2/24/2004 +0200, Gonzalo Camarillo wrote:
>The global identifiers we are looking for do not even need to be routable. 
>That is, it can be a sequence of bits that identify a UA. SIP provides 
>other mechanisms to be able to contact such a UA.

then, it requires something like LSI (local scope.) But, I was talking
about use of IP address in SIP header.

In multi6 list, christian mentioned that SIP doesn't use FQDN because of
performance/privacy problems (although, it allows change of IP address.)
So, how about using HI instead of IP address in SIP headers? This also
avoids _all_ transport traversal problem by making the NAT to be HIP
aware (STUN does the opposite; also works for UDP only.)

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From: [email-masked] (Gonzalo Camarillo)
Date: Tue Feb 24 04:27:01 2004

Hi,

> performance/privacy problems

SIP uses FQDNs, so I do not understand why somebody would say that it 
does not.

> So, how about using HI instead of IP address in SIP headers? 

This would be a bigger step, which may be taken when HIP is more mature. 
Right now, the only problem they need to resolve is having a globally 
unique identifier for user agents.

Thanks,

Gonzalo

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From: [email-masked] (senthil ayyasamy)
Date: Tue Feb 24 04:37:00 2004

At 12:10 PM 2/24/2004 +0200, Gonzalo Camarillo wrote:
>SIP uses FQDNs, so I do not understand why somebody would say that it does 
>not.

ok. I should have been clear. _I_ was wrong in stating that FQDN is not all
used. I was just talking about SIP's use of IP address. sorry for the
confusion and thanks for your clarification !

anyway, since i misquoted christian, here is the original post:
http://psg.com/lists/multi6/multi6.2004/msg00207.html

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From: [email-masked] (Miika Komu)
Date: Tue Feb 24 08:34:01 2004

>     like ad-hoc, sensor, P2P etc.

This depends on the userspace resolver library that makes the queries. I
am currently experimenting with a "native" HIP resolver which could handle
multiple types of directories. But I really haven't thought about other
other than DNS resolvers yet.

>     model + distributed object look-up for name resolution?

HIP does not currently support multicast. It would be nice research topic
though.

-- 
Miika Komu              [email-masked]          http://www.iki.fi/miika/

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From: [email-masked] (Pekka Nikander)
Date: Sun Feb 29 01:23:02 2004

Gonzalo,

(Sorry for the delay in answering,)

> have a global identifier, so that I can distinguish it from my other 
> SIP devides (like my software based SIP user agent running in my 
> laptop). the relevant drafts are:
>

Looking at Section 3 of this draft:

>    3.1 Characteristics of a GUID
>
>       The idea of a globally unique ID is hardly a new concept. ...
>
>       A common characteristic of these identification numbers is that 
> they
>       have two basic properties:
>
>        - They are unique to the entity they are associated with.
>
>        - A central authority coordinates the assignment of IDs to 
> ensure
>          that no two entities are given the same identifier.

Well, in the case of HIP we do not (necessarily have this).  Central
assigning authority is not currently available, and the HITs are unique
only because the probability of collision is so low.  And even in the
case of two HITs colliding, the actual public keys are very very likely
to be unique.  (If they aren't, the private keys are also the same, and
it is impossible to distinguish between the hosts.  But that is likely
to happen only if we assign multiple public keys to each atom in the
universe.)

>       Note, that there is no requirement that there be any sort of 
> registry
>       that knows which entity has what identifier....
Ok.

>       Sometimes entities need to be able to be identified uniquely, 
> but to
>       have a central authority assign an identifier would be difficult 
> or
>       impossible. In these situations, it is still possible for the 
> entity
>       to assign itself a unique identifier. This can be achieved by 
> using a
>       mechanism that ensures that the odds of any two entities having 
> the
>       same identifier are statistically insignificant.

Just like currently in HIP.

>       An example of this mechanism would be human fingerprints....

The section then gives a fairly simple mechanism of generating
GUIDs using time, space and other attributes as source of randomness.

Hence, just looking at the draft, I think that using HITs instead
would make great sense.  It would give the additional property of
self-authentication.

--Pekka